salt marshes + esturaies

Estuary

Transition between freshwater and marine biomes, where freshwater meets sea

Salt marshes

Communities of emergent herbs, grasses or low shrubs rooted in soils that are alternately inundated and drained by tidal action

Coastal plain estuary

Formed when rising sea level flooded coastal river valleys at the end of last ice age

Tectonic estuary

Sea floods the land due to subsidence of the land

Lagoon estuary

Sandbars parallel to the coastline partially cut off water from the open ocean, collect freshwater from land runoff or rivers

Fjord

Valleys deepened by glaciers and invaded by the sea, often a shallow sill at the mouth restricts water flow between deep fjord and sea

Salinity

Horizontal, vertical and seasonal variability

Causes: freshwater input, evaporation, density differences, tides, seasons

Substrate

Mud

1. Anoxic below surface

2. No attachment points for macroalgae

3. Sediments clog respiratory and feeding structures

4. Nutrient rich - productive but species poor

5. Lots of bacterial respiration

Temperature

Great fluctuation in water, less in mud

Wave action and currents

Fetch: distance the wind can blow is limited by land

Flushing time- time required for a given amount of freshwater to leave the estuary and freshwater to replace it

Estuaries biota

Stenohaline: very narrow salinity tolerance

Euryhaline: broad salinity tolerance

Brackish water

Mixture of freshwater and salt water

Autochthonous production

Algal primary productivity

Generally low in estuaries due to light limitations from turbidity

Allochthonous production

Organic matter produced elsewhere and transported to estuaries, large amounts

Floral composition in esturaries

Limited in number of large plants

Common types: seagrasses, macroalgae, small benthic algae in biofilms, salt marsh plants dominant

Estuarine plankton

Reduced number of species

Lots of Bacteria

Phytoplankton

Zooplankton

Composition and biomass depends on turbulence, turbidity, and flushing rate

Phytoplankton controls

Limited by Nitrogen And Light

Blooms of some algae

Zooplankton controls

Limited by low phytoplankton or by currents

Consume 50-70% of the phytoplankton produciton

Amphidromous

Move into estuaries to grow and feed (nursery)

Estuary adaptations

1. Salinity changes

Animals: osmoconformers (osmotic concentration of their internal fluids flucuates with the environment), osmoregulators (move salts to adjust ions to maintain a favorable water balance), mixed strategy, burrowing or migrating

Plants: succulence strategy (accumulate water), and mechanisms to deal with high salt (salt secreting glands, shedding leaves)

2. Oxygen depletion in mud

Aerenchyma

Air passages bringing oxygen to the roots usually in anoxic sediments

Salt marsh plants

Harsh environment, mostly herbaceous angiosperms, Spartina = cordgrass, Juncus= rush

Rhizome systems that stabilize marsh

Salt marsh animals

Marine: crabs mussels snails amphipods shrimp fish

Terrestrial: insects raccoons birds

Wide distribution of these few species

Little influence of grazers in northern marshes

Salt marsh interactions

Few herbivores

90% of production becomes detritus

Migration in and out

Oyster/mussel beds

Denitrification

Reduce effects of N pollution

Eutrophication

Excess nutrients which leads to excess phytoplankton

Anoxia

Water completely depleted of dissolved oxygen